Genealogical DNA test
From ISOGG Wiki
A genealogical DNA test examines the nucleotides at specific locations on a person's DNA for genetic genealogy purposes. The test results are not meant to have any informative medical value and do not determine specific genetic diseases or disorders; they are intended only to give genealogical information.
The general procedure for taking a genealogical DNA test involves taking a painless cheek-scraping (also known as a buccal swab) at home and mailing the sample to a genetic genealogy laboratory for testing. Some laboratories use mouth wash or chewing gum instead of cheek swabs. Some laboratories, such as the Human Origins Genotyping Laboratory (HOGL) at the University of Arizona, offer to store DNA samples for ease of future testing. All United States laboratories will destroy the DNA sample upon request by the customer, guaranteeing that a sample is not available for further analysis.
Y chromosome DNA (Y-DNA) tests
A man's patrilineal or direct father's-line ancestry can be traced using the DNA on his Y chromosome through Y-STR testing. The Y chromosome, like the patrilineal surname, passes down unchanged from father to son. A man's test results are compared to another man's results to determine the time frame in which the two individuals shared a most recent common ancestor or MRCA. If their test results are a perfect or nearly perfect match, they are related within a genealogical time frame.
Mitochondrial DNA (mtDNA) tests
A person's matrilineal or mother-line ancestry can be traced using the DNA in his or her mitochondria, the mtDNA. mtDNA is passed down by the mother unchanged, to all children. If a perfect match is found to another person's mtDNA test results, one may find a common ancestor in the other relative's (matrilineal) "information table". However, because mtDNA mutations are very rare, the match will not necessarily be within a genealogical time frame.
Autosomal DNA tests
Family Finder and Relative Finder
Geographical origin tests
Some companies use autosomal DNA tests to identify a geographical origin. These tests measure an individual's mixed geographic heritage by identifying particular markers, called ancestry-informative markers or AIM, that are associated with populations of specific geographical areas. The tests' validity and reliability have been called into question but they continue to be popular. Anomalous findings most often result from databases too small to associate markers with all the areas where they occur in indigenous populations.
Autosomal DNA testing purports either to determine the "genetic percentages" of a person's ancestry from particular continents/regions or to identify the countries and "tribes" of origin on an overall basis. Admixture tests arrive at these percentages by examining SNPs, which are locations on the DNA where one nucleotide has "mutated" or "switched" to a different nucleotide. Tests listing geographical places of origin use alleles — individual and family variations on various chromosomes across the genome analyzed with the aid of population databases. As further detailed below, this latter type of test concentrates on standard identity markers, such as the CODIS profile, combined with databases such as OmniPop, ENFSI and proprietary adaptations of published studies. The admixture tests are designed to tell what percentages a person has of ancestry of Native American, European, East Asian, and Sub-Saharan African.
- Bolnick, DA et al. The Science and Business of Genetic Ancestry Testing. Science: Vol 318, 19 October 2007
- Frudakis, T. The Legitimacy of Genetic Ancestry Tests. Science: Vol 319, 22 February 2008
- Beginners' guides to genetic genealogy
- International Society of Genetic Genealogy
- Genographic Project
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